Transmission unit comprising a transmission coil and a temperature sensor

ABSTRACT

The invention relates to a transmitter unit (12) comprising a housing (20), a transmitter coil (18) arranged in the housing (20) for inductively transferring electrical energy to a receiver unit (14) which is provided with a receiver coil (16) and is arranged in the tissue (2) of the body (1) of a patient when the housing (20) having a contact surface (22) is placed on the body (1), and comprising a control device (30) for controlling the operation of the transmitter coil (18). According to the invention, a temperature sensor (26) is provided in the transmitter unit for determining a heating of the tissue (2) of the body (1) caused by the inductive transfer of electrical energy to the receiver unit (14). The invention also relates to methods for determining the temperature (TKorr) of the tissue (2) of a body (1) on a surface (38), by which electrical energy is inductively transmitted for supplying an electrical consumer arranged in the tissue (2) of the body (1), and to a method for inductively transferring electrical energy.

The invention relates to a transmitter unit comprising a housing, comprising a transmitter coil disposed in said housing for inductively transferring electrical energy to a receiver unit, which is disposed in a part of the body of a person, in particular a patient, e.g. in the tissue of a body of a patient, and comprises a receiver coil, when a contact surface of said housing is in contact with the body, and comprising a control device for controlling the operation of the transmitter coil.

The invention also relates to a method for determining the local temperature of a body of a person, in particular a patient, on a surface, e.g. the temperature of the tissue of the body on a surface, through which electrical energy for supplying an electrical consumer disposed in the tissue of the body is inductively transferred and to a method for inductively transferring electrical energy. The invention in particular relates to a method for determining the temperature on a surface in an apparatus for inductively transferring energy. The invention further relates to an apparatus which is operated according to a method according to the invention as well as the use of the method according to the invention.

In the medical field, methods for inductively transferring energy, in which an energy store in the form of a rechargeable battery disposed inside a body can be charged by inductive means, are already well-known in the state of the art (DE 10 2016 106 683 A1). For this purpose, a receiver coil disposed in a receiver unit inside the body of a patient cooperates with a transmitter coil disposed in a transmitter unit outside the body. Between the receiver coil and the transmitter coil, which are positioned at a defined, relatively small distance to one another, there is human tissue or the skin of the patient. During the operation of the transmitter coil, the tissue of the patient between the receiver unit and the transmitter unit is warmed, in particular as a result of thermal losses in the transmitter unit and in the receiver unit. The level of warming is limited for health reasons and may not exceed a certain amount.

The object of the invention is to enable the inductive transfer of electrical energy to a powerful electrical consumer or electrical energy store disposed, for example, in the body of a patient, without damaging the tissue of the patient.

This object is achieved by the transmitter unit specified in claim 1 and the methods specified in claim 18 and claim 20.

Advantageous embodiments of the invention are specified in the dependent claims.

The invention is based on the idea that monitoring the temperature of the surface of a patient in the region of direct contact with the transmitter unit makes it possible to infer information about the warming of the tissue of the patient.

One finding of the invention is that the measurement signals of a temperature sensor, which is disposed as close as possible to the to-be-measured surface, are affected by the inductive transfer of electrical energy. It is evident that, during operation of the transmitter coil, not only the (human) tissue or the skin surface of the patient is warmed, but that the magnetic fields produced by the transmitter coil also warm the temperature sensor or its leads, which results in a measurement error. Taking into account a not-to-be-exceeded (limit) temperature of the tissue in the transfer region of the apparatus, this then means that the operation of the transmitter coil is not optimized yet, or the registered temperature does not correspond to the actual temperature on the to-be-measured surface of the patient.

The invention has the advantage that it makes optimum use of the foreseen (allowable) maximum temperature increase of the tissue of the patient in the effective region of the transmitter unit or the transmitter coil, and thus makes it possible to optimize or maximize the transfer of energy into the receiver coil. This then enables short charging times for an electrical energy store, e.g. in the form of a rechargeable battery, disposed in the body of the patient, for example, or the possibility of reducing the time the externally disposed transmitter unit or transmitter coil is worn on the body.

One idea of the invention is that the component of the warming of the temperature sensor caused by the fields of the transmitter coil of the transmitter unit is taken into account when the temperature of the to-be-measured surface is registered. Taking into account the component of the warming of the temperature sensor caused by the (magnetic) fields emitted by the transmitter coil therefore reduces the temperature on the surface determined by the temperature sensor, which results in longer operating times, and/or makes it possible to set stronger magnetic fields of the transmitter coil, before a specific not-to-be-exceeded temperature limit value on the to-be-measured surface is actually reached.

In a variant of the method as described thus far, it can be provided that the component of the warming of the temperature sensor or its input leads is taken into account as a fixed value resulting from taking into account a given maximum operating time of the apparatus and given environmental parameters. This means that it has been determined, in particular on the basis of series of tests, by what amount of temperature the temperature sensor is warmed when it is exposed to a typical maximum operating time of the transmitter coil, taking into account a typical maximum outside temperature, for example. If this value is 0.8 Kelvin, for example, this maximum temperature increase of the temperature sensor (0.8 Kelvin) is subtracted from the respective value of the temperature on the surface currently registered by the temperature sensor, to thereby infer the actual maximum prevailing temperature on the surface.

In a further variant modified from the variant described above, an actually existing warming of the temperature sensor resulting from the operation of the transmitter coil can be taken into account by determining the component of the warming of the temperature sensor taking into account the registered temperature progression of the sensed surface after the operation of the transmitter coil of the apparatus has been stopped. This means that, after the operation of the transmitter coil of the apparatus is stopped, the temperature sensor continues to register the temperature on the to-be-measured surface and delivers it as input values to the control device of the apparatus. The actually existing temperature on the to-be-measured surface at the time the operation of the transmitter coil is stopped can be inferred using the temperature drop that occurs over time and is caused, on the one hand, by the no longer occurring transfer of heat into the human body and, on the other hand, by the heat dissipation from the temperature sensor.

In a further development of this method, it is provided that the operation of the transmitter coil is stopped periodically. The temperature on the to-be-measured surface of the patient can thus be monitored throughout the entire charging phase or the phase in which energy is transferred from the transmitter coil to the receiver coil.

There are a number of different ways to infer the actual temperature of the to-be-measured surface. In a first, particularly preferred method, the component of the warming of the temperature sensor caused by the operation of the transmitter coil is determined on the basis of a mathematical function taking into account known parameters of the temperature sensor and, if applicable, environmental parameters. Known parameters of the temperature sensor are in particular understood to be its heat storage capacity, its placement inside the housing of the transmitter unit, and thus its heat dissipation or cooling. Environmental parameters are in particular understood to be the external ambient temperature in the region of the transmitter unit and, if applicable, the current body temperature of the patient. The mentioned parameters of the temperature sensor and the apparatus or the housing of the apparatus and the ambient temperature can be brought into a mathematical relationship, for example using series of tests, such that, for example, a specific cooling function of the temperature sensor is established at a specific ambient temperature. This function can therefore be used to extrapolate or estimate the actual temperature on the to-be-measured surface at the time the transmitter coil is switched off.

In an alternative configuration of the method, however, it can also be provided that the temporal progression of the temperature registered by the temperature sensor after the transmitter coil is switched off is compared to curve progressions stored in the control device and, if it matches or approximates a stored curve progression, the actual temperature in the region of the to-be-measured surface at the time the transmitter coil is switched off can be inferred.

For a further optimization of the energy transfer to shorten charging times or to achieve the highest possible charging rates for the electrical energy store disposed in the patient, it is proposed that the apparatus for inductively transferring energy is controlled on the basis of the determined temperature, and that the transmitter coil is periodically not operated to avoid the occurrence of excessively high temperatures, wherein the duration of the operating breaks of the transmitter coil is based on the determined temperature on the surface. This means that the length of the operating breaks is selected to be such that they last only until the registered temperature is at a specific minimum separation from the limit value. The temperature on the to-be-measured surface is thus always kept just below the limit temperature, which overall enables an optimization of the energy transfer. Alternatively, it is also possible to throttle or adjust the transmission power to keep the temperature constant without operating breaks.

The invention also includes an apparatus for inductively transferring energy comprising a transmitter coil disposed in a housing, wherein the housing can be positioned at least in indirect contact with the to-be-measured surface, and wherein the apparatus is operated according to a method, in which the component of the warming of the temperature sensor is determined taking into account the registered temperature progression of the sensed surface after the operation of the transmitter coil of the apparatus is stopped. According to the invention, this apparatus comprises a temperature sensor, which can be exposed to the electromagnetic field of the transmitter coil so that said sensor is disposed in an operative connection with said coil. The apparatus can comprise an algorithm for determining the component of the warming of the temperature sensor or its input leads caused by the transmitter coil.

For the sake of making the apparatus as compact as possible, it is preferably provided that the temperature sensor is of an SMD design.

Lastly, the invention also includes the use of a method according to the invention as described thus far for determining the skin and/or tissue temperature in a human body during a transfer of energy into the human body, in particular with a VAD (ventricular assist device) system.

Further advantages, features and details of the invention emerge from the following description of preferred design examples. These are shown schematically in the drawings and are described below.

The figures show:

FIG. 1 an apparatus for inductively transferring energy comprising a transmitter coil and comprising a temperature sensor, which is used for inductively transferring energy into a receiver unit having a receiver coil in a VAD system disposed in a human body;

FIG. 2 a first diagram with the temporal progression of a temperature T registered by the temperature sensor in the apparatus for inductively transferring energy and with a limit temperature T_(Grenz), and

FIG. 3 a second diagram with the temporal progression of a temperature T registered by the temperature sensor in the apparatus for inductively transferring energy and with a limit temperature T_(Grenz).

The same elements or elements having the same function are provided with the same reference signs in the figures.

FIG. 1 shows the essential components of an apparatus 10 for inductively transferring energy on a receiver unit 14 disposed in the body 1 of a patient and having a receiver coil 16 in a highly simplified manner. The apparatus 10 is in particular a component of a cardiac support system in the form of a so-called ventricular assist device system (VAD system) 100. The VAD system 100 in particular includes a pump disposed in the body 1 of the patient, which supports the patient's heart function. In the body 1 of the patient, this pump is operated with electrical energy from an electrical energy store not shown in FIG. 1, e.g. a rechargeable battery, which is connected to the receiver unit 14. This electrical energy store has to be charged due to the energy consumption of the pump. By inductively transferring energy into the receiver unit 14 by means of the apparatus 10, the electrical energy store connected to the receiver unit 14 is charged.

The apparatus 10 comprises a transmitter unit 12 outside the body 1 of the patient and the receiver unit 14 with the receiver coil 16 disposed inside the body 1 of the patient. It should be noted that the receiver unit 14 may in principle comprise a plurality of receiver coils 16.

Between the transmitter unit 12 and the receiver unit 14 there is human tissue 2 or the skin of the patient. The receiver coil 16 is disposed in operative connection with the electrical energy store to be charged. The receiver coil 16 cooperates with a transmitter coil 18 disposed in the transmitter unit 12. The transmitter coil 18 is disposed inside a housing 20 of the transmitter unit 12, whereby the housing 20 is disposed at least in indirect contact with the body 1 or the tissue 2 in the region of a contact surface 22 of the housing 20.

The transmitter coil 18 has a coil winding 17, which comprises conductor loops disposed around a coil axis 19 that passes through the contact surface 22. The coil winding 17 of the transmitter coil 18 is located on a transmitter coil carrier 21, which extends in a planar manner and through which the coil axis 19 passes, and which has a carrier surface that faces the contact surface 22 of the housing 20 for the coil turns of the transmitter coil 18.

To operate the apparatus 10, it is also necessary for the receiver coil 16 and the transmitter coil 18 to be aligned with one another in order to be able to produce a magnetic field when current is supplied to the transmitter coil 18. The field lines 24 of this magnetic field, which are shown in FIG. 1, lead to the induction of an electrical voltage and thus to the flow of an electrical current in the receiver coil 16, which can then be used to charge the electrical energy store.

During operation of the transmitter coil 18, the tissue 2 of the body 1 located between the transmitter unit 12 and the receiver unit 14 is warmed by the loss-related warming of the transmitter unit 12 and the receiver unit 14. This warming of tissue 2 has to be limited to avoid physical impairments or damage and/or to comply with legal standards.

For this purpose, it is provided that the temperature of the tissue 2 in the region of contact of the housing 20 of the transmitter unit 12 with the tissue 2 is monitored by means of a temperature sensor 26 in the region of a measurement surface 38 on the surface of the tissue 2.

The temperature sensor 26 is disposed in the housing 20 of the transmitter unit 12 on a side 23 of the transmitter coil 18 facing the contact surface 22.

To make the design as compact as possible, it is in particular provided that the temperature sensor 26 is designed as an SMD component or an SMD assembly. The temperature sensor 26 is connected to a control device 30 of the transmitter unit 12 via an electrical lead 28. The control device 30 is also used to control the transmitter coil 18 via a lead 32. A further lead 34 connects the control device 30 to a further temperature sensor 36, which is configured to register the ambient temperature outside the transmitter unit 12.

As can be seen in FIG. 1, both the temperature sensor 26 and, if applicable, the lead 28 are disposed in operative connection with the magnetic field lines 24 of the transmitter coil 18. As a result, during operation of the transmitter coil 18, not only the tissue 2 is warmed, in particular by the lost heat from the transmitter unit 12 and the receiver unit 14, but also the temperature sensor 26 or the lead 28, in particular by the magnetic field of the transmitter coil 18, which can lead to the temperature sensor 26 heating up more than the surrounding tissue 2. This in turn has the consequence that the temperature increase of said components leads to a measurement error, which manifests itself in that the temperature T registered by the temperature sensor 26 in the region of the measurement surface 38 is falsified or increased by the measurement error.

To detect or take into account this measurement error or to register the actual temperature T on the measurement surface 38 of the body 1, the transmitter coil 18 is operated in a specific manner. For clarification, reference is made to FIG. 2.

FIG. 2 shows the temperature T registered by the temperature sensor 26 in the apparatus 10 at the time t as a curve progression A. The temperature sensor 26 transmits the temperature T registered at the time t to the control device 30.

The temperature T increases slightly in the period between t₀ and t₁. The increase in temperature T can be explained by the fact that, during operation of the transmitter coil 18, both the temperature in the tissue 2 and the temperature in the temperature sensor 26 or the lead 28 is increased by the effect of the temporally changing magnetic field produced by the transmitter coil 18, which causes eddy currents. However, the temperature T is below a limit temperature T_(Grenz) that has to be observed. At the time point t₁, the operation of the transmitter coil 18 is now stopped by the control device 30. The curve progression A then shows that the temperature T, which continues to be registered by the temperature sensor 26 and delivered to the control device 30 as an input quantity, decreases with the decay curve 40.

The curve progression A after the time point t₁ results from both the now absent warming of the tissue 2, or its cooling, and from the heat dissipation or cooling of the temperature sensor 26 and the lead 28.

An algorithm with a mathematical function is stored in the control device 30 of the transmitter unit 12 or the apparatus 10, which makes it possible to infer the actual temperature T in the region of the measurement surface 38 at the time point t₁ based on the values of the temperature T after the time point t₁, for example by extrapolation from the cooling rate V_(K) at a time point t₂ after the time point t₁. This makes use of the fact that, due to its size, the temperature sensor 26 has a significantly lower heat storage capacity than the surrounding tissue 2 and the surface of the housing 20. As a result, there is a dynamic drop in the temperature T immediately after the transmitter coil 18 is switched off at the time point t₁. Once this temporary equalization process is completed at the time point t₂, the temperature sensor 26 registers the actual temperature T of the tissue 2, because the low heat storage capacity of the temperature sensor 26 has been “discharged”. The mentioned extrapolation of the cooling curve at the switch-off time t₁ can therefore be used to infer the actual temperature at the switch-off time t₁. The additional warming of the temperature sensor 26 is thus taken into account or eliminated.

Alternatively, it can be provided that the curve progression A after the time point t₁ is compared to curve progressions stored in the control device 30, and, if it matches or approximates a stored curve progression, the respective temperature T_(Korr) at the measurement surface 38 of the body 1 at the time point t₁ is inferred. The difference between the corrected temperature T_(Korr) on the measurement surface 38 and the temperature T registered at the time point t₁ is the component ΔW caused by the warming of the temperature sensor 26 and the lead 28.

As soon as the temperature T on the measurement surface 38, which has been corrected by the amount of warming of the temperature sensor 26 or the lead 28 caused by the operation of the transmitter coil 18, has been determined, the control device 30 again actuates the transmitter coil 18 in order to enable a further transfer of energy. In order to enable continuous monitoring of the (actual) temperature T on the measurement surface 38, the switching off or switching on of the transmitter coil 18 as described thus far is preferably carried out periodically, i.e. at regular intervals.

FIG. 3 shows a diagram that illustrates a simplified measurement procedure. Here, the temperature T registered by the temperature sensor 26 is again shown over the time t. A continuous, i.e. uninterrupted, operation of the transmitter coil 18 is assumed. The values of the temperature T transmitted by the temperature sensor 26 to the control device 30 are indicated by the curve progression A. The curve progression A_(K) shows a corrected curve progression A taking into account a fixed value ΔF as the component ΔW, which is assumed to be the maximum possible measurement error resulting from the warming of the temperature sensor 26 and the lead 28 due to the warming caused by the operation of the transmitter coil 18. In other words, this means that the control device 30 assumes that the temperature T calculated using the A_(K) is the highest possible temperature that can be present on the measurement surface 38.

Of course, in both methods it is respectively assumed that the operation of the apparatus 10 or the transmitter coil 18 is stopped when a limit temperature T_(Grenz) is approached, for example until the determined temperature T has a specific separation from the limit temperature T_(Grenz).

The methods as described thus far can be altered or modified in a variety of ways without departing from the idea of the invention. It should in particular be noted that the described methods are not limited to use in a VAD system 100.

In summary, the following preferred features of the invention should in particular be noted:

A transmitter unit 12 comprises a housing 20 and a transmitter coil 18 disposed in said housing 20 for inductively transferring electrical energy to a receiver unit 14, which is disposed in the tissue 2 of the body 1 of a patient and comprises a receiver coil 16, when a contact surface 22 of said housing 20 is in contact with the body 1. The transmitter unit 12 comprises a control device 30 for controlling the operation of the transmitter coil 18. The transmitter unit comprises a temperature sensor 26 for determining a local warming of the body 1 caused by the inductive transfer of electrical energy into the receiver unit 14. The invention also relates to methods for determining the temperature (T_(Korr)) of a body 1 on a surface 38 through which electrical energy for supplying an electrical energy store or an electrical consumer disposed in the body 1 is inductively transferred and to a method for inductively transferring electrical energy.

The invention relates, in particular, to the aspects specified in the following clauses:

-   -   1. Method for determining the temperature (T) on a surface (38)         in apparatus (10) for inductively transferring energy, wherein         the apparatus (10) comprises a transmitter coil (18) disposed in         a housing (20) and the housing (20) is disposed at least in         indirect contact with the to-be-measured surface (38), and         comprising a temperature sensor (26) for registering the         temperature (T) of the surface (38), wherein the temperature         sensor (26) and, if applicable, the electrical lead (28) of said         sensor is disposed in operative connection with the transmitter         coil (18), such that, during operation of the transmitter coil         (18), the temperature sensor (26) and, if applicable, the         electrical lead (28) of said sensor is warmed by the fields         emitted by the transmitter coil (18), so that the         temperature (T) registered by the temperature sensor (26)         includes a component (ΔW) that results from the warming of the         temperature sensor (26) and, if applicable, the electrical lead         (28) of said sensor by the transmitter coil (18), and wherein         the component (ΔW) resulting from the transmitter coil (18) is         taken into account in the registering of the temperature (T) of         the measurement surface (38).     -   2. Method according to clause 1, characterized in that that the         component (ΔW) is taken into account as a fixed value (ΔF),         which is obtained by taking into account a given maximum         operating time of the apparatus (10) and given environmental         parameters.     -   3. Method according to clause 1, characterized in that the         component (ΔW) of the warming is determined taking into account         the registered temperature progression (A) of the sensed surface         (38) after the operation of the transmitter coil (18) of the         apparatus (10) is stopped.     -   4. Method according to clause 3, characterized in that the         operation of the transmitter coil (18) is stopped periodically.     -   5. Method according to clause 3 or 4, characterized in that the         component of the warming (ΔW) is determined on the basis of a         mathematical function, taking into account known parameters of         the temperature sensor (26), such as its heat storage capacity         storage capacity, and, if applicable, environmental parameters.     -   6. Method according to clause 3 or 4, characterized in that the         component of the warming (ΔW) is based on a comparison of the         temperature progression (A) on the sensed surface (38) with         stored curve progressions.     -   7. Method according to any one of clauses 1 to 6, characterized         in that the apparatus (10) for inductively transferring energy         is controlled on the basis of the determined temperature (T) and         the transmitter coil (18) is periodically not operated to avoid         the occurrence of excessively high temperatures (T), wherein the         duration of the operating breaks of the transmitter coil (18) is         based on the determined temperature (T) on the surface (38).     -   8. Apparatus (10) for inductively transferring energy,         comprising a transmitter coil (18) disposed in a housing (20),         wherein the housing (20) can be positioned at least in indirect         contact with a to-be-measured surface(38), wherein the apparatus         (10) is operated according to a method according to any one of         Clauses 3 to 7, characterized in that a temperature sensor (26)         is disposed in operative connection with the transmitter coil         (18), and that the apparatus (10) comprises an algorithm for         determining the component (ΔW) of a warming of the temperature         sensor (26) and, if applicable, the lead (28) of said sensor         caused by the fields emitted by the transmitter coil (18).     -   9. Apparatus according to clause 8, characterized in that the         temperature sensor (26) is of an SMD design.     -   10. Use of the method according to any one of clauses 1 to 7 for         determining the skin and/or tissue temperature of a human body         (1) during an energy transfer in the human body (1), in         particular in a VAD system (100).

List of Reference Signs

-   1 Body -   2 Human tissue -   10 Apparatus -   12 Transmitter unit -   14 Receiver unit -   16 Receiver coil -   17 Coil winding -   18 Transmitter coil -   19 Coil axis -   20 Housing -   21 Transmitter coil carrier -   22 Contact surface -   23 Side -   24 Field line -   26 Temperature sensor -   28 Electrical lead -   30 Control device -   32 Lead -   34 Further lead -   36 Further temperature sensor -   38 Measurement surface -   40 Decay curve -   42 Section -   100 Ventricular assist device (VAD) system -   A Curve progression -   A_(K) Corrected curve progression -   T Temperature -   T_(Grenz) Limit temperature -   T_(Korr) Corrected temperature -   t Time -   V_(K) Cooling rate -   ΔW Component -   ΔF Fixed value 

1.-27. (canceled)
 28. A transmitter unit comprising: a housing comprising a transmitter coil configured to inductively transfer electrical energy to a receiver unit disposed in a part of a body of a patient in response to a contact made between a contact surface of the housing and the body of the patient, the receiver unit comprising a receiver coil; a temperature sensor configured to determine an increase in local temperature of the body caused by the inductive transfer of electrical energy to the receiver unit; and a control device configured to control operation of the transmitter coil based at least in part on the increase in local temperature of the body, wherein the control device stores a temperature determination routine configured to determine a local temperature at a surface of the body based at least in part on temperature measurement signals of the temperature sensor; wherein the temperature determination routine is configured to stop the operation of the transmitter coil at a first time point and contains an algorithm configured to calculate the local temperature based at least in part on a decay curve determined based at least in part on the temperature measurement signals from the temperature sensor after the first time point, wherein the temperature determination routine is configured to account for warming of the temperature sensor caused by eddy currents.
 29. The transmitter unit of claim 28, wherein the transmitter coil is disposed in the housing and the temperature sensor is positioned between the transmitter coil and the contact surface.
 30. The transmitter unit of claim 29, wherein the transmitter coil comprises conductor loops configured to form a coil winding around a coil axis that passes through and orthogonal to the contact surface.
 31. The transmitter unit of claim 30, wherein the conductor loops are disposed on or in a transmitter coil carrier extending in a planar manner and parallel to the contact surface.
 32. The transmitter unit of claim 31, wherein the transmitter coil carrier comprises a carrier surface which faces the contact surface of the housing.
 33. The transmitter unit of claim 28, wherein the temperature determination routine is configured to account for an operating state of the transmitter coil.
 34. The transmitter unit of claim 28, wherein the algorithm is configured to calculate the local temperature at the surface of the body based at least in part on extrapolation of the decay curve from a second time point following the first time point to the first time point.
 35. The transmitter unit of claim 34, wherein the algorithm is configured to linearly extrapolate the progression of the decay curve from a second time point to the first time point.
 36. The transmitter unit of claim 28, wherein the algorithm is configured to subtract a fixed correction value from temperature values corresponding to the temperature measurement signals.
 37. The transmitter unit of claim 28, wherein the control device stores a shutdown routine configured to stop the operation of the transmitter coil, wherein the shutdown routine is configured to prevent or reduce the inductive transfer of electrical energy to the receiver unit when the local temperature determined by the temperature determination routine exceeds a threshold value.
 38. The transmitter unit of claim 28, wherein the temperature sensor is at least one of: a surface-mount-device component, a temperature-dependent measuring resistor, and a thermocouple.
 39. A system comprising: a temperature sensor; a transmitter coil; a memory storing computer-readable instructions; a processor configured to communicate with the temperature sensor, the transmitter coil, and the memory, wherein the computer-readable instructions, when executed, cause the processor to: prevent an inductive transfer of electrical energy from the transmitter coil at a first time point; determine temperatures of a surface of a body at a plurality of time points following the first time point; determine a decay curve based at least in part on the temperatures measured at the plurality of time points following the first time point; and calculate a local temperature of the surface of the body based at least in part on the decay curve and an algorithm configured to account for an effect of the inductive transfer of electrical energy from the transmitter coil to an electrically powered device.
 40. The system of claim 39, wherein the algorithm is configured to determine the local temperature of the surface of the body at least in part by extrapolating a progression of a section of the decay curve from a second time point following the first time point to the first time point.
 41. The system of claim 40, wherein the algorithm is configured to extrapolate the progression of the section of the decay curve based at least in part on a comparison of the decay curve with one or more decay curve progressions stored in the memory.
 42. The system of claim 40, wherein the algorithm is configured to linearly extrapolate the progression of the decay curve from the second time point to the first time point.
 43. The system of claim 40, wherein the preventing the inductive transfer of electrical energy from the transmitter coil at the first time point, the measuring the temperatures at the surface at the plurality of time points following the first time point, the determining the decay curve from the temperatures measured at the plurality of time points following the first time point, and the calculating the local temperature at the surface of the body based at least in part on the decay curve and the algorithm configured to account for an effect of inductive transfer of electrical energy from the transmitter coil to the electrically powered device are repeated continuously.
 44. A method for determining a local temperature at a surface of a human body, wherein electrical energy for an electrical energy storage or an electrically powered device disposed in the body is inductively transferred through the surface, the method comprising: preventing an inductive transfer of the electrical energy at a first time point; determining temperatures measured at the surface at a plurality of time points following the first time point; determining a decay curve based at least in part on the temperatures measured at the surface at the plurality of time points following the first time point; and calculating the local temperature at the surface based at least in part on the decay curve and an algorithm accounting for an effect of the inductive transfer of electrical energy to the electrical energy storage or the electrically powered device.
 45. The method of claim 44, wherein the algorithm is configured to extrapolate a progression of a section of the decay curve from a second time point following the first time point to the first time point.
 46. The method of claim 45, wherein the algorithm is configured to extrapolate the progression of the section of the decay curve based at least in part on a comparison of the decay curve to one or more decay curve progressions stored in a data memory.
 47. The method of claim 45, wherein the algorithm is configured to linearly extrapolate the progression of the decay curve from the second time point to the first time point. 